agent: Avoid tight timer tick when possible.

* agent/gpg-agent.c (need_tick): Evaluate whether the short-phase
handle_tick() is needed.
(handle_connections): On each cycle of the select loop, adjust whether
we should call handle_tick() or not.
(start_connection_thread_ssh, do_start_connection_thread): Signal the
main loop when the child terminates.
* agent/call-scd.c (start_scd): Call interrupt_main_thread_loop() once
the scdaemon thread context has started up.

--

With this change, an idle gpg-agent that has no scdaemon running only
wakes up once a minute (to check_own_socket).

Thanks to Ian Jackson and NIIBE Yutaka who helped me improve some of
the blocking and corner cases.

Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Gbp-Pq: Topic gpg-agent-idling
Gbp-Pq: Name 0003-agent-Avoid-tight-timer-tick-when-possible.patch

diff --git a/agent/call-scd.c b/agent/call-scd.c
index 15a2ba52950750dbb69a59ed29323fc6c74cba8a..0bf603084d236446aa3a8719172771eebe7d374d 100644 (file)
--- a/agent/call-scd.c
+++ b/agent/call-scd.c
@@ -407,7 +407,9 @@ start_scd (ctrl_t ctrl)
 
   primary_scd_ctx = ctx;
   primary_scd_ctx_reusable = 0;
-
+  /* notify the main loop that something has changed */
+  interrupt_main_thread_loop ();
+  
  leave:
   xfree (abs_homedir);
   if (err)

diff --git a/agent/gpg-agent.c b/agent/gpg-agent.c
index 73cd560aab3b7abf36b95ebf57d0b0d88b9dbf75..b33de7d3947a6a34d2603ad773a7de223df31cd8 100644 (file)
--- a/agent/gpg-agent.c
+++ b/agent/gpg-agent.c
@@ -2279,6 +2279,26 @@ create_directories (void)
 }
 
 
+static int
+need_tick (void)
+{
+#ifdef HAVE_W32_SYSTEM
+  /* We do not know how to interrupt the select loop on Windows, so we
+     always need a short tick there. */
+  return 1;
+#else
+  /* if we were invoked like "gpg-agent cmd arg1 arg2" then we need to
+     watch our parent. */
+  if (parent_pid != (pid_t)(-1))
+    return 1;
+  /* if scdaemon is running, we need to check that it's alive */
+  if (agent_scd_check_running ())
+    return 1;
+  /* otherwise, nothing fine-grained to do. */
+  return 0;
+#endif /*HAVE_W32_SYSTEM*/
+}
+
 
 /* This is the worker for the ticker.  It is called every few seconds
    and may only do fast operations. */
@@ -2337,7 +2357,7 @@ agent_sigusr2_action (void)
 
 #ifndef HAVE_W32_SYSTEM
 /* The signal handler for this program.  It is expected to be run in
-   its own trhead and not in the context of a signal handler.  */
+   its own thread and not in the context of a signal handler.  */
 static void
 handle_signal (int signo)
 {
@@ -2618,7 +2638,8 @@ do_start_connection_thread (ctrl_t ctrl)
 
   agent_deinit_default_ctrl (ctrl);
   xfree (ctrl);
-  active_connections--;
+  if (--active_connections == 0)
+    interrupt_main_thread_loop();
   return NULL;
 }
 
@@ -2698,7 +2719,8 @@ start_connection_thread_ssh (void *arg)
 
   agent_deinit_default_ctrl (ctrl);
   xfree (ctrl);
-  active_connections--;
+  if (--active_connections == 0)
+    interrupt_main_thread_loop();
   return NULL;
 }
 
@@ -2883,6 +2905,9 @@ handle_connections (gnupg_fd_t listen_fd,
          thus a simple assignment is fine to copy the entire set.  */
       read_fdset = fdset;
 
+      /* avoid a fine-grained timer if we don't need one: */
+      timertbl[0].interval.tv_sec = need_tick () ? TIMERTICK_INTERVAL : 0;
+
       /* loop through all timers, fire any registered functions, and
          plan next timer to trigger */
       npth_clock_gettime (&curtime);